Evapotranspiration, the biggest cause of water loss on earth


Evapotranspiration, the biggest cause of water loss on earth

We can see rain and snow, but we can’t see the biggest cause of water loss in almost every area on earth: evapotranspiration. Reliable data is lacking on this invisible water loss largely because evapotranspiration is so difficult to measure.

Accurate measurements of evapotranspiration can be obtained from advanced hydrometeorological equipment or from direct measurements of water content changes in the soil. The first type of measurements have as a disadvantage that the representative area of the measurement changes according to wind speed, wind direction and land use. This disadvantage does not count for direct measurements of soil moisture change. The most accurate way of measuring soil moisture content change is by weighing a representative undisturbed soil column with high frequency.

The biggest handy lysimeter in the world

The patented, high-quality, Eijkelkamp Smart Lysimeter provides these measurements, by using a (two-pronged) system of weighing cells to measure water content changes and sensors to mimic the surrounding soil water conditions in an isolated undisturbed  soil column. In this way accurate data on the soil water content and water fluxes (including evapotranspiration and groundwater recharge) are obtained. By installing additional sensors, extra information can be gathered on vertical gradients of soil moisture, matric potential, temperature and electrical conductivity. The use of a telemetric system provides a high temporal sampling resolution.

Complete Water Balance for Rijnland Water Authority
“Why did we acquire three Eijkelkamp Smart Lysimeter stations?” Jan Willem van Kempen, Water Level Manager, and René van der Zwan, Advisor Policy and Research, of Rijnland Water Authority (the Netherlands), explain: “On the one hand, our work involves operational water level management, and on the other hand it is clear that water level management in part is under pressure due to climate change.” Read more or watch the video.

It all starts with an in-depth installation

On-site installation of the Eijkelkamp Smart Lysimeter can be done by our experienced and skilled Technical Projects team. During installation the Eijkelkamp Lysimeter Installation Toolkit will be used to minimize disturbance of the surroundings.

Evapotranspiration data in the cloud

As a telemetric system is offered, the data visualization will be done by means of a web portal, offering visualization of the measurement location in terms of pictures and graphics, data graphical representation of measurements values, alarm generation, options to export data to CSV-format and system status (measurement interval, send interval, battery status, etc.).


  • Scientific support from partners
  • Patented design
  • Undisturbed 20" soil monolith (sample)
  • Sensors in soil monolith
  • Infrared sensors for integrated metering
  • Local data logging via SDI-12
  • Telemetric communications web portal
  • Product training
  • Installation tools
  • Installation service


  • Climate research
  • Agriculture
  • Nature management
  • Reference measurement for remote sensing
  • Scientific research
  • Water Boards
  • Drinking water companies 

Watch the video on Royal Eijkelkamp’s YouTube channel

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